Human A&PBIO 304 · American River College ← Week 07 pre-work

BIO 304 · Week 07 · Interactive Workbook

Gas Exchange & Transport

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Part 1 of 4 · Recall

Fill in the blanks

Type the term that completes each statement, using the word bank. Pull it from memory first.

Word bank

Right shift = unload O₂HypercapniaPeripheral chemoreceptorsDissolved in plasma (~7-10%)Mixed venous bloodAir at sea levelTissueOxygenated Hb at lungsMethemoglobinemiaHb saturation (SaO₂)Reversed at lungsPontine centersCO₂ diffusesBound to hemoglobin (~98.5%)Fetal Hb (HbF)

  1. PO₂ ~160 mmHg, PCO₂ ~0.3 mmHg
  2. PO₂ ~40 mmHg, PCO₂ ~46 mmHg
  3. PO₂ ~40 mmHg, PCO₂ ~45 mmHg
  4. capillary → alveolus (down 6 mmHg gradient; CO₂ more soluble)
  5. each Hb binds up to 4 O₂; oxyhemoglobin
  6. percent of Hb sites with O₂ bound; pulse oximetry reads it
  7. high CO₂, low pH (Bohr effect), high temperature, high 2,3-BPG
  8. higher O₂ affinity than adult Hb; pulls O₂ across placenta
  9. CO₂ more soluble than O₂
  10. HCO₃- moves back in; reforms CO₂ for exhalation
  11. releases CO₂ for expiration
  12. fine-tune rhythm
  13. carotid & aortic bodies; sense O₂, CO₂, pH; respond to severe hypoxia
  14. high PaCO₂; ventilation failure
  15. Fe in Hb oxidized to Fe³⁺; cannot bind O₂

Define it: high-yield vocabulary

Write a clear definition in your own words for each term.

  1. Partial pressure
  2. Respiratory membrane
  3. Oxyhemoglobin
  4. Oxygen-hemoglobin dissociation curve
  5. Right shift
  6. Bicarbonate transport
  7. Chloride shift
  8. Central chemoreceptor
  9. Peripheral chemoreceptor
  10. Hypoxemia
  11. Hypercapnia
  12. Respiratory acidosis

Part 2 of 4 · Anatomy lab

Draw and label

Box A. Alveolus and tissue gas exchange

Directions

  1. Draw two panels side by side: the alveolus (LEFT) and a body tissue (RIGHT).
  2. Left panel: an alveolus with air inside. PO2 in alveolus is about 104 mmHg, PCO2 is about 40 mmHg. Wrap the alveolus with a pulmonary capillary. Blood entering the capillary has PO2 about 40, PCO2 about 45. Show O2 diffusing INTO the blood and CO2 diffusing OUT to the alveolus. By the time blood leaves, PO2 is ~100 and PCO2 is ~40.
  3. Right panel: a tissue cell. Inside the cell, PO2 is about 40 and PCO2 is about 45 (because the cell is consuming O2 and making CO2). Wrap the tissue with a systemic capillary. Blood entering has PO2 ~100, PCO2 ~40. Show O2 diffusing INTO the tissue and CO2 diffusing OUT to the blood. By the time blood leaves, PO2 is ~40, PCO2 is ~45.
  4. Add labels: external respiration (lungs), internal respiration (tissues). Note: diffusion goes down partial pressure gradients.
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Box B. Hemoglobin transports O2

Directions

  1. Draw a hemoglobin molecule schematically: four globin chains (subunits) clustered, each containing a heme group with a central iron (Fe). Label one heme.
  2. Show the hemoglobin in two states: deoxyhemoglobin (no O2 bound) and oxyhemoglobin (4 O2 molecules bound, one per heme).
  3. Draw a hemoglobin LOADING in the pulmonary capillary (high PO2): O2 binds.
  4. Draw a hemoglobin UNLOADING in a tissue capillary (low PO2): O2 dissociates.
  5. Note: hemoglobin shows cooperative binding (first O2 makes the next easier to bind), producing the S-shaped saturation curve.
  6. Below, note three factors that promote unloading: low pH, high PCO2, high temperature (the Bohr effect). These are all features of active tissue.
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Structures to label

Label each on your drawing.

  1. Alveolus
  2. Pulmonary capillary
  3. PO2 (high in alveolus, low in tissue)
  4. PCO2 (low in alveolus, high in tissue)
  5. External respiration
  6. Internal respiration
  7. Hemoglobin
  8. Globin chain
  9. Heme group
  10. Iron (Fe)
  11. Oxyhemoglobin
  12. Deoxyhemoglobin
  13. Bohr effect

Part 3 of 4 · Physiology lab

Reason it through

A. Oxygen-hemoglobin dissociation curve

1. At PO2 = 100 mmHg (lung capillary), what is hemoglobin saturation?
2. At PO2 = 40 mmHg (tissue capillary at rest), what is saturation?
3. Why is the curve S-shaped (sigmoidal) rather than linear?
4. Predict the direction the curve SHIFTS when blood pH drops, PCO2 rises, or temperature rises. What does the shift accomplish at the tissue?
5. A patient is given high-FiO2 oxygen therapy, raising arterial PO2 from 100 to 200 mmHg. Predict the change in hemoglobin saturation (it doesn't double).

B. Synthesis

1. Carbon monoxide (CO) binds hemoglobin with about 200 times the affinity of O2 and forms carboxyhemoglobin. Predict the effects on (a) hemoglobin saturation, (b) the dissociation curve, (c) O2 delivery to tissues. Why is CO poisoning so dangerous even at low concentrations?
2. Most CO2 in the blood is transported as bicarbonate (HCO3-), formed inside red blood cells by carbonic anhydrase. Trace this pathway: CO2 enters the RBC, becomes carbonic acid, then dissociates. Where does the H+ go, and where does HCO3- go?
3. An athlete in heavy exercise has muscle PCO2 high, pH low, and temperature elevated. Predict (using the Bohr effect) what happens to hemoglobin's affinity for O2 at the muscle, and why this is exactly what the muscle needs.

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